A friend of one of the people responsible for the Dec. 2 mass shooting in California has been charged in connection with the attacks, as well as for plotting other unrelated terrorist acts.

Enrique Marquez Jr. was arrested Thursday, the Department of Justice said in a news release.

The 24-year-old is accused of unlawfully buying two assault rifles that his longtime friend, Syed Rizwan Farook, and Farook’s wife, Tashfeen Malik, used to kill 14 people and injure 21 more during a holiday party for Farook’s coworkers on Dec. 2 in San Bernardino. He was also accused of playing a role in plotting attacks with Farook in 2011 and 2012, plans they later abandoned.

Marquez was expected to appear in federal court later Thursday.

The official charges against him included conspiring to provide material support to terrorists, making a false statement about purchasing firearms, and immigration fraud, prosecutors said.

“While there currently is no evidence that Mr. Marquez participated in the Dec. 2, 2015 attack or had advance knowledge of it, his prior purchase of the firearms and ongoing failure to warn authorities about Farook’s intent to commit mass murder had fatal consequences,” U.S. Attorney Eileen M. Decker said in a statement announcing the arrests.

Prosecutors said Marquez moved to Riverside around 2005 and lived next door to Farook, who introduced him to Islam. Farook told Marquez about his radical views, prosecutors said, and Marquez converted to the religion in 2007. By 2011, prosecutors said Marquez “spent most of his time” with Farook, listening, watching and reading various radical Islamic materials.

Prosecutors said Farook and Marquez began planning terrorist attacks in 2011, and that Marquez admitted the attack was “designed to maximize the number of casualties that could be inflicted.” Marquez allegedly told prosecutors he and Farook wanted to throw pipe bombs into a cafeteria at Riverside Community College, where they had both studied, and shoot people as they fled. Prosecutors also allege Marquez told them about a terrorist plot involving pipe bombs and guns that would have targeted a stretch of California Route 91 during rush-hour traffic.

Prosecutors allege that Marquez bought two assault rifles between 2011 and 2012 that he claimed were for himself, but he was actually going to give to Farook for those attacks. Marquez allegedly told prosecutors he agreed to buy the guns because he appeared Caucasian and Farook appeared Middle Eastern. Marquez is also accused of buying explosive smokeless powder to aid “his and Farook’s plans to create bombs and commit mass killings,” according to the news release.

Prosecutors allege Marquez went to firing ranges with Farook to practice for those attacks in early 2012, but Marquez “distanced himself” from Farook in late 2012 after other people in Southern California were arrested for terrorism charges in November.

Authorities said that forensic tests confirmed two of the guns Farook and Malik used in San Bernardino were the ones Marquez allegedly purchased.

Additionally, prosecutors charged Marquez with entering into “a sham marriage with a member of Farook’s extended family so that she could obtain legal status in the United States.” Marquez’s alleged wife paid him $200 a month, prosecutors claim.

In one more detail, prosecutors illuminated published media reports saying that Malik pledged allegiance to the leader of the Islamic State on the morning of the attack.

In the news release, prosecutors allege “a Facebook account associated with Malik searched for” Islamic State materials that morning, and that the account posted “We pledge allegiance to Khalifa bu bkr al bhaghdadi al quraishi,” which prosecutors believe is the publicized pledge.

The FBI said the investigation into the San Bernardino shooting is ongoing.